A Pluto Primer

05Jul15

A Pluto Primer

In about 9 days, when NASA’s New Horizons spacecraft zips past Pluto, everyone’s going to be a Pluto expert. Everybody’s favorite dwarf planet is going to the top news story for a few days. We’ll learn more about Pluto in the 85 hours around July 14th than we’ve learned in the 85 years since it’s discovery by Clyde Tombaugh in 1930.

And, in about two weeks, everyone will be sick to death of Pluto. Well, not everyone, but a lot of people will be Pluto-ed out.

Here’s the basic information you need to know about this little ball of rock at the edge of the solar system.

Pluto:
• is smaller than Earth’s moon – about two-thirds the size;
• was named for the ruler of the underworld in Greek mythology;
• has five of its own moons – Charon, Styx, Nix, Hydra and Kerberos and they are all named after characters of the underworld in Greek and Roman mythology;
• the Disney dog was named for the planet;
• is really cold. It’s surface temperature is around minus 380 degrees Fahrenheit.

For a moment, let’s think about what’s about to happen. Scientists began to seriously conceive of a mission to Pluto in the 1980s and, after several false starts – New Horizons actually launched in 2006.

A funny thing happened on the way to the ninth planet. It got downgraded from planet to dwarf planet. The International Astronomical Union (IAU )decided on a definition of “planet” that Pluto did not meet. As a result, it was reclassified as a dwarf planet.

Nonetheless, Pluto was still out there and New Horizons was well on it’s way by the time the IAU voted Pluto out of the planet club.

Fast forward about 10 years, and New Horizons is still out there – speeding along at nine miles per second. Thanks, in part, to a gravity assist by Jupiter, New Horizons is the fastest spacecraft ever launched.

The problem with Pluto is that it’s far away. Very far away.

The moon is our nearest neighbor at about 240,000 miles. Suppose you could drive a car to the moon (Let’s ignore all the things that make that impossible and focus on just distance and time) at 65mph. How long would it take?

If you could drive to Pluto the same way – 65 miles per hour, 24 hours a day – it would take about 6,500 years.

So, Pluto is really out there. It’s about 30 times as far from the sun as Earth. It’s so far out there that the Hubble Space Telescope can’t get a decent picture of it and that’s the reason we sent New Horizons. Pluto is so far away, the only way to learn about it, was to send a robot.

Pluto isn’t just a dwarf planet, it’s actually a really complicated system of celestial objects. Pluto has five moons. Its largest, Charon, is so large that it doesn’t even orbit Pluto. Charon and Pluto orbit a common center of gravity between the two objects and the other four moons orbit that point as well.

Pluto and Charon are a binary system with the other moons orbiting the two “dwarf planets” in the middle. The two bodies are what’s called tidally locked which means they keep the same face toward each other at all times. If you could stand on Pluto, Charon would seem to forever hover over you. Aren’t you glad you paid attention in geometry, now?

Included with its suite of cameras and scientific instruments are nine very human objects. These include two US flags, a CD-ROM of over 400,000 names of people who wanted to participate in this voyage of discovery and another CD-ROM with pictures of the team that conceived, devised and built the spacecraft.

There is a small piece of Spaceship One – the first privately funded manned spacecraft to fly in space. There are state quarters from Florida (where New Horizons was launched) and Maryland (where the spacecraft was built), there is a 1991 US postage stamp declaring “Pluto: Not Yet Explored,”

Finally, there is a small canister containing some of the ashes of Clyde Tombaugh containing the inscription: